Patent GB-155568-A (GB)
Abstract: 155,568. Automatic Telephone Manufacturing Co., (Assignees of Wicks, J.). Dec. 13, 1919, [Convention date]. Automatic and semi-automatic exchange systems; metering and coin-freed systems; party-line systems.-When a subscriber on an automatic exchange makes a local connexion, his meter is operated once (or a single pre-payment coin is collected) at the termination of the conversation, but when he connects himself to a trunking operator, who extends the call to another exchange, the meter is operated a variable number of times (or a variable number of coins are collected) by the operator as soon as the wanted subscriber answers. In the case of unsuccessful calls, currents of a different nature are transmitted in order to render the meter inoperative or to rebate the coin. In the case of trunk calls from subscribers who are on a measured-service agreement, the operator gets a special tone signal, indicating that she must operate her metering and coin-collecting key; for this purpose, the switching-relays of the line switches of such subscribers are connected to battery through the secondary of a tone apparatus, while in the case of subscribers on a flat-rate agreement the connexion is to battery direct. The circuit-operations at the exchange are the same whether the calling substation is equipped with a meter or with prepayment apparatus; sub-stations of these two types may even be associated with the same party-line, as shown in Fig. 1. A relay repeater set D, Fig. 1, is associated with each first-selector trunk to control the metering &c. currents. Substation metering arrangements, A<1>, Fig. 1. At the first operation of the impulse-sender S, a circuit is closed by springs 6 through relay 2, springs 5 and the switch-hook H to line 21, which is connected to battery at the exchange. Relay 2 breaks its own circuit, locks itself mechanically, and connects line 22 to ground through a polarized relay 4 and the meter M. This circuit remains closed throughout the call, but is of two high resistance to interfere with impulse transmission or conversation. The current which now flows in the line is too weak to actuate either the meter M or the relay 4. If the call is a local one, the circuits remain in this condition until the conversation is over. When the subscriber A<1> hangs up his instrument, a battery of higher voltage is momentarily connected to line at the exchange, and the meter is actuated. The meter contact 7 momentarily connects the lower winding of a relay 3 to line, and the relay 3 unlatches relay 2, so that the substation is restored to normal condition. If the call had been unsuccessful, a highvoltage battery of reverse polarity would have been momentarily connected to line when the subscriber hung up; in that case the polarized relay 4, energizing more rapidly than the meter M, would have short-circuited the meter and closed a circuit for the disconnecting-relay 3. In the case of a trunk call, the operator, as soon as she has got the wanted subscriber, may operate the motor repeatedly, by causing the repeated application of a high voltage on the line; for in this case, since the switch-hook is still in its raised position. the operation of the meter does not energize the disconnecting-relay 3, this relay being differentially wound and its upper winding being now energized, in parallel with its lower winding, through the meter contact 8 and the switch-hook. Substation prepayment arrangements, A, Fig. 1. The prepayment arrangements are of a known kind, requiring the preliminary insertion of a coin to remove a short-circuit from the impulse-sender S<1>, and comprising a polarized magnet P responsive to high voltage of direct or reverse polarity to collect or return the coin. General operation. Local call. When the calling subscriber A or A<1> lifts down his receiver, the hne switch C connects the line to an idle firstselector trunk in known manner, energizing relays 53, 54, 55 and the upper (polarizing) windings of relays 59, 60. These relays, however, are adjusted so as to be actuated only when both their windings are energized in the same direction. The line relay 101 of the first selector E, Fig. 2, is now energized over wire 93, lower winding of relay 59, windings of relays 58, 57, and wire 95. The relay 57 is energized, but the marginal relay 58 does not receive enough currcnt, and relay 59 does not receive current of the right polarity. The numerical impulses are repeated in the trunk 93, 95 by contact 70 of relay 53 to operate the selectors E, F, I, which select the wanted line in known manner. During the passage of impulses, relay 56 is energized and short-circuits relays 57, 58, 59 and the inductance 62 (which is normally in the calling line circuit) to reduce the impedance of the impulse, circuits to a minimum. When the subscriber A<2> answers the call. the current in the trunk 93, 95 is reversed by the relay 150, Fig. 2, and the polarized relay 59 responds and energizes relay 52, which locks itself up. After conversation, when the calling subscriber hangs up, the successive de-energization of relays 53, 54, 55 leads to the momentary energization of relays 56, 51, and line 22 is momentarily connected through contacts 66, 67 to the lamp L<3> and high-voltage battery B<1>, to operate the meter M or collect a coin. If the call had been an unsuccessful one, the relay 52 would not have been energized and the line 22 would have been momentarily connected to the reverse high-voltage battery B<2> to return the coin or restore the substation circuits without operating the meter. Trunk call. When the subscriber A or A<1> calls the single digit 0, he is connected by the selector E to the first idle trunk of a series such as O leading to jacks at operators' positions. Relay 203 lights a call-lamp L', which is extinguished by relay 205 when the operator answers the call. Relay 205 also disconnects the upper winding of relay 203 from line, so as to de-energize relay 57, Fig. 1, which removes a short-circuit from the secondary s of a transformer, of which the primary p is connected through relay 24 and magnet 23 to a tone apparatus Q. The operator, hearing the tone signal, knows that the call is from a subscriber on a measured-service agreement, and presses the key TK, which energizes the self-locking relay 204, which restores the connexion between the upper winding of relay 203 and line, so as to re-energize relay 57 and cut off the tone signal. After obtaining the wanted connexion, the operator presses the key CK as often as the charge requires, energizing relav 202 which connects the high-voltage battery B<3> to the upper side of the trunk, energizing the marginal relay 58, Fig. 1. Relay 58 energizes relay 51 (which disconnects but keeps energized the line relay 53) and removes a short-circuit from the lower winding of polarized relay 60, which now responds and connects the high-voltage battery B<1> through contacts 84, 67, 66 to line 22 to operate the meter M or collect a coin. The relay 61, which is energized in this circuit, grounds the trunk 95 to short-circuit the lower winding of relay 203, which relapses and closes the circuit of a lamp L<2>, which indicates to the operator that the meter at the calling station is being energized, or that a coin is being collected. If for any reason the meter M had not been connected to the line 22, or if the subscriber had failed to insert a coin for collection, the relay 61 would not be energized and the lamp L<2> would not light up. If the operator wishes to return a coin, she can do so by pressing a key RK, which energizes relay 201 to throw the reverse high-voltage battery B<4> into circuit. In this case the polarized relay 60 is not energized, so that the reverse battery B<2> is connected to line. In the case of meter substations, the disconnexion of the meter by the relay 3 takes place after the subscriber has hung up, the battery B<2> being momentarily connected to line in the same way as. after an unsuccessful local call.